This application makes reference to and claims all benefits accruing under 35 U.S.C. Section 119 from an application entitled xe2x80x9cLong Period Fiber Grating Packagexe2x80x9d filed in the Korean Industrial Property Office on Aug. 29, 2000 and there duly assigned Ser. No. 2000-50504.
1. Field of the Invention
The present invention relates generally to packaging of long-period fiber gratings and, in particular, to a long-period fiber grating package that is packaged such that its reflection wavelength is temperature-independent.
2. Description of the Related Art
Fiber gratings are well known in optical fiber communication systems. The function of a fiber grating is to selectively remove or reflect light at a specific wavelength, by inducing a periodic change in the refractive index of the fiber using a UV (Ultra Violet) laser. In contrast, a long-period fiber grating with a periodic spacing, which is typically in the hundreds of micrometers, can be used as a gain flattening filter for an EDFA (Erbium Doped Fiber Amplifier) as it removes light at a specific wavelength by mode conversion. That is, long-period grating removes light without reflection by coupling light from a core mode (or guided mode) to a cladding mode (or non-guided mode). Hence, the central wavelength and the extinction ratio of the long-period fiber gratings are determined by mode coupling between the core mode and the cladding mode. However, long-period gratings exhibit high temperature sensitivity.
To eliminate the influence on the refractive index change by ambient temperatures, a double cladding technique has been employed to reduce the temperature sensitivity. That is, an additional cladding is applied on the outer surface of a primary cladding to be temperature-independent. However, protection of wavelengths against temperature change requires the difficult task of accurately controlling the refractive index distribution and the amount of dopant concentration in the fiber. Therefore, there is a need for a temperature compensating package used to stabilize the temperature sensitivity of long-period gratings.
The present invention provides a long-period fiber grating package that ensures the usage of long-period gratings without temperature control.
According to an aspect of the present invention, there is provided along-period package that protects fiber gratings against ambient influences, such as moisture. The inventive package for holding long-period fiber gratings is partially removed to which a recoating is applied thereto in order to stabilize the optical characteristics of the long-period fiber gratings. Thereafter, a silica glass tube is fixed around the recoating to protect the long-period fiber gratings from an ambient environment.
According to another aspect of the invention, there is provided a method of packaging long-period fiber gratings and includes the following steps: providing an optical fiber comprising a core and a cladding; removing a section of the cladding along the fiber; transmitting light passing through an amplitude mask to form the long-period fiber gratings into the removed section of the fiber; forming a recoating layer around the removed section of the fiber to maintain optical characteristics thereon; inserting a silica glass tube around the recoating layer for protecting the long-period fiber gratings from ambient environment; and, inserting a protective layer around the silica glass tube for protecting against external stresses.